This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The high excitation energy transfer efficiency observed in photosynthetic organisms relies on the optimal pigment-protein binding geometry in the individual protein complexes and also on the overall architecture of photosystems. In green sulfur bacteria, the membrane-attached Fenna-Matthews-Olson (FMO) antenna protein functions as a "wire" to connect the large peripheral chlorosome antenna complex with the reaction center (RC), which is embedded in the cytoplasmic membrane. Energy collected by the chlorosome is funneled through the FMO to the RC. Significant effort has been expanded to understand the relationship between structure and function of the individual isolated particles. The question of how the FMO protein interacts with the membrane and the chlorosome in vivo to maintain a specific architecture to ensure the highly efficient energy transfer pathway, however, has not been answered.